A 12-GHz Transformer Feedback Class-F₂,₃ Voltage-Controlled Oscillator Using Noise Circulating With FoM of 190.5 dBc/Hz

A 12-GHz transformer feedback Class-F
_2,3
voltage-controlled oscillator (VCO) using noise circulating is proposed in this letter. Transformer feedback is utilized in the proposed VCO to achieve Class-F
_2,3
resonant impedance control at the VCO output and tail current transistor input. Also, the noise contribution of the tail current transistor is further reduced by partially circulating its noise into itself. The proposed VCO is fabricated in 40-nm CMOS process with 0.04-mm
²
core area. Experimental results show that the frequency tuning range of the VCO is 11.74–12.63 GHz. The VCO achieves phase noise of −120.2 dBc/Hz at 1-MHz offset frequency at 12 GHz with figure of merit (FoM) of 190.5 dBc/Hz and FoM
$_{T}$
of 187.8 dBc/Hz, and consumes 13.23 mW from a 1.1-V supply.